1. Field of the Invention
This invention/relates to a resin composition adapted to treat the surface of a material so as to make it water- and ink-repellent and, more particularly, to a photocurable epoxy resin composition adapted to form a patterned film coat by irradiating ultraviolet rays. More specifically, the present invention relates to an alkylsiloxane-containing epoxy resin composition and to a surface modifying method for treating the surface of a base material by using such a composition as well as to a liquid-jet recording head treated for ink-repellence and also to a liquid-jet recording apparatus using such a recording head.
2. Related Background Art
Methods for modifying the surface of a base material that needs to be water-resistant or ink-repellent in order to make it to be satisfactorily so by applying a water-repellent paint thereto are widely known in various industrial fields and a variety of resin materials and paints have been developed for this purpose. For instance, fluoroolefins and fluorine-containing paints having one or more than one perfluoro-groups in a molecule are thermally and chemically highly stable and also remarkably resistant against weather, water, chemicals and solvents. Additionally, they show good mold release characteristics, a good abrasion resistance and a good water repellency so that they find applications in various fields.
Meanwhile, liquid-jet recording heads adapted to eject liquid droplets through small ejection ports and cause them to adhere to a recording medium such as a sheet of paper so as to record or form an image thereon are recently required to be able to eject smaller liquid droplets, be driven with a higher head oscillation frequency and have a greater number of nozzles in order to achieve a higher level of performance. Therefore, such a recording head is required than ever to have a nozzle surface that is treated and modified in order to be maintained in a same state.
However, according to the results of intensive research efforts of the inventors of the present invention, it is difficult to accurately treat the surface of a nozzle selectively or in the form of a pattern by using any known materials so that ink may not adhere thereto. This is because firstly, while a substance having one or more than one photosensitive functional groups in a molecule has to be used as surface treatment material for treating the surface of the nozzle in the form of a pattern so that it may operate like photoresist, it is highly difficult to design a molecule having such groups and showing a water-repellent/ink-repellent effect at the same time.
Secondly, if the surface of the nozzle can effectively be treated by means of a known fluorine-containing substance, the film coat of the substance is required to show a structure that can maintain the treated condition of the surface for a prolonged period of time. If such a substance is available and can be used to treat the surface of a nozzle in the form of a pattern, it will be highly valuable for treating an ink-jet printing head for the reasons pointed out below.
In an ink-jet recording system of ejecting droplets of ink through nozzles for recording, it is highly desirable that the ejection ports (openings) of the system have the following characteristic features.
(1) The remaining part of the ink column formed outside the nozzle that has been turned to droplets are quickly put back into the nozzle.
(2) The ink droplets adhering to the surface can easily be wiped away by a cleaning operation.
(3) The surface is hardly scraped or damaged because of the rub resistance of the surface when they are wiped away in a cleaning operation or when the recording paper is moved along the surface.
(4) A meniscus is formed at the surface position of the nozzle in the repeated process of droplet formation and ink refill.
(5) The direction of the normal to the meniscus agrees with that of the droplet ejection.
(6) The interfacial tension and hence the contact angle of the ink has to be large enough for forming a meniscus if the ink shows low surface tension or under low negative pressure.
The reason why the above listed so many features are required for the ejection ports is that, if recording liquid such as ink adheres to and near the ejection ports, the direction in which the liquid droplets ejected from the ejection ports of the liquid-jet recording head fly can become diverted to make it difficult to print highly accurately and degrade the printing performance of system. Means have been proposed to make the surface of an ejection port and its vicinity repellent to liquid in order to prevent liquid from adhering to the ejection port and its vicinity to make the liquid droplets ejected therefrom to be diverted from the right direction. For example, Japanese Patent Application Laid-Open No. 2-39944 discloses a method of treating the surface of the ejection port by means of a polymer material having fluoroacetyl groups and silazane groups in order to make it repellent to ink.
Meanwhile, as a result of the increasing demand for sophisticated printers utilizing liquid-jet recording systems for recording images, the recording liquid to be used for such recording systems is also required to show sophisticated characteristic features. More often than not, the recording liquid to be used for such recording systems is chemically regulated so as to be basic with a pH value between 7 and 11 in order to make it stable. Then, the printer members that may be brought into contact with the recording liquid are required to be highly resistant against alkali and hydrolysis.
However, if a recording liquid containing a polar organic solvent is used with the water-repellent agent and/or the recording solution shows such a high pH value, the water-repellent agent applied to the surface of the ejection port in order to satisfy the above requirements can damage the film forming property of the agent and the tight adhesion of the agent relative to the surface of the ejection port as it comes to contact with the solvent of the recording liquid and the polar organic solvent used for the recording liquid. Then, the coat of the water-repellent agent can be peeled off to lose the water repellence of the surface.
Therefore, it is an object of the present invention to provide a siloxane-containing epoxy resin composition that can be suitably used for a water-repellent agent or a water-repellent coating to be applied to an area of a member that can be brought into contact with one or more than one solutions and/or materials such as polar organic solutions that can damage the film-forming effect and the adhesion of the water-repellent agent. It is another object of the present invention to provide a siloxane-containing epoxy resin composition adapted to surface modifying treatment for maintaining the treated surface constantly in a same state. Still another object of the present invention is to provide an ink-jet recording head and a liquid-jet recording apparatus having a printing head whose nozzle surface is free from adhesion of ink as the surface of the base material of the head is treated by a siloxane-containing epoxy resin composition. Such an ink-jet printing head and a liquid-jet recording apparatus provide the advantage that the surface of the printing head is free from adhesion of ink if held in contact with recording liquid (ink) for a prolonged period of time so that consequently the ink droplets shot out of the printing head show excellent impact precision and provide an excellent printing quality.
According to the invention, the above objects and other objects of the invention can be achieved by providing an alkylsiloxane-containing epoxy resin composition containing at least an alkylsiloxane-containing epoxy resin having two or more than two alkylsiloxane groups and two or more than two cyclic aliphatic epoxy groups in a molecule and a cationic polymerization catalyst, in particular, wherein the alkylsiloxane-containing epoxy resin is a cyclic aliphatic epoxy resin (A) having a structural unit expressed by general formulas (a) and (b) below. In other aspects of the present invention, there are provided a surface modifying method, an ink-jet recording head and a liquid-jet recording apparatus using such an alkylsiloxane-containing epoxy resin composition. 
wherein
x=1 to 50, y=2 to 100, n is an integer of 2 to 100,
R1 and R2 are independently H or CH3,
R3 and R4 are independently CH3 or phenyl,
R5 is CH2, xe2x80x94CH2CH2xe2x80x94 or xe2x80x94CH2CH(CH3)xe2x80x94.